Passenger vehicles having convertible tops that can be raised to cover the passenger compartment and lowered to open the compartment predate the closed sedan type of vehicle and have been manufactured for many years. Recently, vehicles having convertible tops have become more popular with purchasers because of their ability to quickly convert from a closed vehicle to an open roadster by lowering the top. Consequently, automobile manufacturers are manufacturing a greater variety of this type vehicle.
The usual convertible top comprises an articulated top frame that supports a fabric cover. The frame includes a plurality of spaced transverse bows interconnecting articulated side rails that support the fabric cover. The rear of the cover is attached to the vehicle body or, in some cases, to a movable rear bow. The front edge of the cover is attached to the front bow, called the top header.
The top header engages the top of the vehicle windshield frame, or windshield header, in top raised position. Header latches clamp the headers together and compress a seal between them. One type of latch that is quite popular and has been used for many years is shown in U.S. Pat. No. 3,216,763 to Heincelman. This type of latch utilizes a J-hook that is mounted by a linkage on the side rail adjacent the top header. The J-hook is operated by a manual handle to engage a pin or abutment on the windshield header.
The operating handle is pivoted to the side rail and stores within the side rail when the latch is closed to latch the top to the windshield header. The handle is pulled away from the side rail to disengage the J-hook from the abutment and unlatch the top from the windshield header. The J-hook mounting linkage enables subsequent storage movement of the handle to withdraw the J-hook within the side rail to facilitate storage of the top after lowering.
Upon unlatching and handle storage, the top is folded and lowered into a storage area located behind the passenger compartment. This action may be accomplished manually or by a power operator, usually a hydraulic unit that includes a hydraulic pump that drives a pair of hydraulic cylinders which lower the top.
The top is raised by reversing the pump to operate the hydraulic cylinders to unfold the top until the top header is in close proximity to the windshield header. The latch handles are then operated to engage the J-hooks with the abutments to compress the seal and secure the headers together.
One requirement of convertible vehicles is that the top cover fit snugly on the frame to present a smooth, sleek appearance. This snug fit also reduces the vehicle's coefficient of drag, which affects gasoline mileage which is now a critical vehicle attribute due to federally-mandated CAFE requirements. A snug fit is accomplished by stretching the cover taut over the frame. Cover stretching occurs at the end of the top raising cycle by fully extending the top frame and operating the header latches.
When a power-operated top is fully raised, the fabric cover is stretched when the hydraulic cylinders fully extend the frame linkage to move the top header into close proximity to the windshield header at the end of the cycle. When the hydraulic pump is turned off, hydraulic pressure quickly diminishes in the cylinders and the top "springs back" as the stretched fabric relaxes, moving the headers apart. The top header must then be manually forced down onto the windshield header to enable the latches to be closed. Since this action requires stretching the fabric cover, a significant amount of manual effort is required to close the latches.
This problem is exacerbated during cooler weather when the top fabric stiffens, requiring increased effort to manually stretch the cover fabric to engage the headers, followed by added effort to close the latches. The added manual effort required to accomplish top latching can be quite aggravating to the vehicle owner. The conventional manual latch usually includes an over-center operation that also requires significant manual effort to unlatch.
Power latches have been devised to eliminate the manual effort required to latch the top. However, they are expensive and complex. Examples of power latches are shown in U.S. Pat. Nos. 3,425,742 to Rauber, Jr., 3,443,834 to Andres, 4,819,983 to Alexander et al, and 4,830,426 to Schlachter et al. Consequently, most convertible tops feature manual latches, the operation of which are plagued by the problem described above.
It is desirable to provide a power header latch for a convertible top that eliminates the manual effort required to latch the top and is simpler and more effective than currently available latches.